Steady-state and nanosecond time-resolved fluorescence methods will be used to investigate the kinetics of excited-state processes of interest in biology. Fluorescence decay, time-resolved emission spectra and time-resolved fluorescence emission anisotropy will be used to study solvent relaxation, proton transfer, energy transfer and rotational motion of fluorophores. Instrumental methods for obtaining the required data and computational procedures for data analysis will be improved. Fluorophores will be studied in solution and when bound to proteins and membrane systems. The fluorescence of tryptophan peptides and tryptophan in proteins will be investigated. Fluorescence decay will be used to uncover microheterogeneity. Information will also be obtained about excited state interactions between tryptophan and solvent molecules. Decay of the fluorescence emission anisotropy will be used to study the rotational behavior of proteins and peptides as well as segmental motion of tryptophan residues. A general aim of the studies is to discover in what way dynamic interactions on the nanosecond time scale are related to the functions of membranes and proteins.